"I have no words, it is too big. I say I can understand their pain because as a mother I feel it too,” she said.

“But I don't even have the courage to compare my pain to theirs. It's as if I were ashamed to say 'I'm also a mother, I'm also suffering.”

Collina said she had tried to keep her son from falling under the sway of Islamic State ideology, but the Internet and his London friends changed him.

"When children make mistakes, parents always feel some guilt. But I did my best, and I think he was worn down on the inside," she said. Collina lives near the northern city of Bologna.

"We always kept track of his friends and made sure he didn't fall in with the wrong people. But he had Internet and that's where everything comes from," she said.

She said she last spoke to her son two days before the attack and that in retrospect she realises it was a “goodbye call".

“Even though he didn't say anything in particular, I could hear it in his voice,” she told L’Espresso.

Zaghba was stopped at the airport in Bologna in 2016 when he was trying to get to Syria via Turkey, city prosecutor Giuseppe Amato told broadcaster Radio24 on Tuesday.

Italian media said Zaghba was born in the Moroccan city of Fez in 1995 but had broken off relations with his Moroccan father. He lived in Morocco for much of his life but made short visits to his mother.